Update how knotd read json config file
Update how knotd read json config file

Knotd used to have its own function to read configuration info from
json file, now it uses a json-c fuction json_object_from_file.

CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source